From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754632Ab3CKVfY (ORCPT ); Mon, 11 Mar 2013 17:35:24 -0400 Received: from li9-11.members.linode.com ([67.18.176.11]:52651 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753234Ab3CKVfW (ORCPT ); Mon, 11 Mar 2013 17:35:22 -0400 Date: Mon, 11 Mar 2013 17:35:20 -0400 From: "Theodore Ts'o" To: Bryan Whitehead Cc: linux-kernel@vger.kernel.org Subject: Re: ext4 change in v3.3-rc2 broke user space Message-ID: <20130311213520.GE15478@thunk.org> Mail-Followup-To: Theodore Ts'o , Bryan Whitehead , linux-kernel@vger.kernel.org References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 11, 2013 at 02:03:51PM -0700, Bryan Whitehead wrote: > > The change is about a year old now but it is finally making its way > into distribution binaries. As a user it sucks because "ext4" the > "stable" fs basically breaks. Fortunately for myself I've used xfs as > suggested by GlusterFS (older versions stated ext4/ext3 was fine). > However, there are many installs (particularly older installs) that > used ext4 and are finding they must now run outdated old kernels until > they can completely reinstall their gluster cluster with non-ext4 > underlying filesystems. GlusterFS is doing something fundamentally buggy; it is assuming that high bits of the value returned "telldir" are zero. This is inherently non-portable. This change was used to avoid hash collision causing problems for applications using telldir/seekdir() on very large file systems. So the question was whether it was important to fix a bug for well behaved, non-buggy applications, or to not fix this bug to accomodate a buggy application (namely, Gluster). There were some questions going back and forth about whether Gluster could work around this non-potable, buggy use of telldir()/seekdir(), and that's why nothing had been done for a while. What we'll probably do to accomodate Gluster is to create a new ext4-specifical ioctl(), which allows the process to get the old telldir cookie format (i.e., EXT4_IOC_IM_A_BUGGY_APPLICATION :-). - Ted